Printers are usually manufactured with tractor or pinwheel type paper feed devices for feeding continuous form type printout paper through the printer, or with a friction roll type paper feed device for feeding cut forms, such as letterheads, individual order forms, or the like through the printer. Some printers are manufactured and sold with one type of paper feed device built into the printer and another type of paper feed device can be purchased and attached to the printer. However, the attachable or "add on" paper feed device is usually not as efficient as the paper feed device which is built into the printer and may require some mechanical skill to attach the alternate paper feed device to the printer.
Various known types of attachable paper feeding devices are shown in prior patents. For example, the printer of U.S. Pat. No. 4,341,480 is manufactured with tractors for normally feeding a continuous form type of paper through the printer. An "add on" type friction roll feed attachment is disclosed in this patent and is provided for converting the continuous form printer into a discrete sheet form printer. U.S. Pat. No. 2,355,668 is directed to a printer which is manufactured with a rotary platen normally adapted to feed cut form paper through the printer. This patent discloses a pinwheel paper feeding attachment which can be attached to the printer so that edge perforated continuous forms can be fed through the printer. U.S. Pat. No. 4,058,196 is directed to a printer with interchangerble paper feed modules, each of which includes a cylindrical platen with the paper engaging and being partially wrapped around the cylindrical platen. One of the paper feed modules includes tractor feeds and the other of the paper feed modules includes pinwheel feeds, and both of which feed edge perforated continuous forms.
While the paper feed devices disclosed in these patents do permit the feeding of various types of papers, and thereby provides the printer with greater versatility, the printer is primarily designed to feed a particular type of paper. The attachments which are provided to permit other types of paper to be fed are usually not as reliable as the paper feeding device which is built into the printer, and these alternate paper feeding attachments may cause feeding problems. Also, the paper feeds of these patents direct the paper at least partially around a cylindrical platen and this type of curved paper path can cause misalignment of multiple part forms.